13 research outputs found
Energy and momentum dependence of nuclear short-range correlations - Spectral function, exclusive scattering experiments and the contact formalism
Results of electron-induced one- and two-nucleon hard knockout reactions,
and , in kinematics sensitive to nuclear short-range
correlations, are studied using the nuclear contact formalism. A relation
between the spectral function and the nuclear contacts is derived and used to
analyze the dependence of the data on the initial energy and momentum of the
knocked-out proton. The ratio between the number of emitted proton-proton pairs
and proton-neutron pairs is shown to depend predominantly on a single ratio of
contacts. This ratio is expected to present a deep minima in the initial energy
and momentum plane, associated with the node in the proton-proton wave
function. The formalism is applied to analyze data from recent He and
C electron-scattering experiments performed at Jefferson laboratory.
Different nucleon-nucleon potentials were used to asses the model-dependence of
the results. For the ratio of proton-proton to proton-neutron pairs in He,
a fair agreement with the experimental data is obtained using the two
potentials, whereas for the ratio of proton-proton pairs to the total
knocked-out protons in C, some of the features of the theory are not
seen in the experimental data. Several possible explanations for this
disagreement are discussed. It is also observed that the spectral function at
specific domains of the momentum-energy plane is sensitive to the
nucleon-nucleon interaction. Based on this sensitivity, it might be possible to
constrain the short range part of the nuclear potential using such experimental
data
Short range correlations and the isospin dependence of nuclear correlation functions
Pair densities and associated correlation functions provide a critical tool
for introducing many-body correlations into a wide-range of effective theories.
Ab initio calculations show that two-nucleon pair-densities exhibit strong spin
and isospin dependence. However, such calculations are not available for all
nuclei of current interest. We therefore provide a simple model, which involves
combining the short and long separation distance behavior using a single
blending function, to accurately describe the two-nucleon correlations inherent
in existing ab initio calculations. We show that the salient features of the
correlation function arise from the features of the two-body short-range
nuclear interaction, and that the suppression of the pp and nn pair-densities
caused by the Pauli principle is important. Our procedure for obtaining
pair-density functions and correlation functions can be applied to heavy nuclei
which lack ab initio calculations.Comment: 5 pages, 4 figure
Quasi-elastic polarization-transfer measurements on the deuteron in anti-parallel kinematics
We present measurements of the polarization-transfer components in the
H reaction, covering a previously unexplored kinematic
region with large positive (anti-parallel) missing momentum, , up
to 220 MeV, and . These measurements, performed
at the Mainz Microtron (MAMI), were motivated by theoretical calculations which
predict small final-state interaction (FSI) effects in these kinematics, making
them favorable for searching for medium modifications of bound nucleons in
nuclei. We find in this kinematic region that the measured
polarization-transfer components and and their ratio agree with the
theoretical calculations, which use free-proton form factors. Using this, we
establish upper limits on possible medium effects that modify the bound
proton's form factor ratio at the level of a few percent. We also
compare the measured polarization-transfer components and their ratio for H
to those of a free (moving) proton. We find that the universal behavior of
H, He and C in the double ratio
is maintained in the positive
missing-momentum region
Exclusive studies on short range correlations in nuclei
Short Range Correlations (SRC) are brief fluctuations of high relative momentum nucleon pairs. Properties of SRC have important consequences for nuclear physics, high energy physics, atomic physics, and astrophysics. SRC pairs form some of the densest states of cold matter achievable on Earth, making them an ideal system to study the partonic and nucleonic degrees of freedom in nuclear systems. Hard exclusive breakup reactions, where high-energy probes scatter on SRC pairs, are used to study such properties of SRC pairs as isospin decomposition, nuclear mass and asymmetry dependence, c.m. momentum distribution. Thomas Jefferson National Accelerator Facility (JLab) plays a key role in the SRC program. CLAS (CEBAF Large Acceptance Spectrometer), located in Hall B at JLab, has almost 4π coverage and is capable of measuring exclusive reactions of the type A(e, e’pp). We will discuss the recent experimental results from JLab and future experiments planned at JLab as well as at JINR
Exclusive studies on short range correlations in nuclei
Short Range Correlations (SRC) are brief fluctuations of high relative momentum nucleon pairs. Properties of SRC have important consequences for nuclear physics, high energy physics, atomic physics, and astrophysics. SRC pairs form some of the densest states of cold matter achievable on Earth, making them an ideal system to study the partonic and nucleonic degrees of freedom in nuclear systems. Hard exclusive breakup reactions, where high-energy probes scatter on SRC pairs, are used to study such properties of SRC pairs as isospin decomposition, nuclear mass and asymmetry dependence, c.m. momentum distribution. Thomas Jefferson National Accelerator Facility (JLab) plays a key role in the SRC program. CLAS (CEBAF Large Acceptance Spectrometer), located in Hall B at JLab, has almost 4π coverage and is capable of measuring exclusive reactions of the type A(e, e’pp). We will discuss the recent experimental results from JLab and future experiments planned at JLab as well as at JINR
The symmetry energy γ parameter of relativistic mean-field models
The relativistic mean-field models tested in previous works against nuclear matter experimental values, critical parameters and macroscopic stellar properties are revisited and used in the evaluation of the symmetry energy γ parameter obtained in three different ways. We have checked that, independent of the choice made to calculate the γ values, a trend of linear correlation is observed between γ and the symmetry energy () and a more clear linear relationship is established between γ and the slope of the symmetry energy (L 0). These results directly contribute to the arising of other linear correlations between γ and the neutron star radii of and , in agreement with recent findings. Finally, we have found that short-range correlations induce two specific parametrizations, namely, IU-FSU and DD-MEδ, simultaneously compatible with the neutron star mass constraint of and with the overlap band for the region, to present γ in the range of. ©2018 Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Sciences and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.CNPq - Brazil (300602/2009-0)CNPq - Brazil (306786/2014-1